# Compute the surface charge density on the belt

• Black-Mind
In summary, the conversation is about calculating the surface charge density on a charge belt that is traveling at 40m/s with a current of 100microA. The suggested answer is 5 microC/m2, but the exact method of calculation is unclear. The conversation ends with the suggestion to draw a diagram to visualize the charge passing by in a given time interval.

#### Black-Mind

I need the answer to this question

A charge belt, 50cm wide, travels at 40m/s between a source of charge and a charging object at a rate corresponding to 100microA . Compute the surface charge density on the belt

Some one told me the answer may be 5 microC/m2 but how ??

You will need to put in some effort if you want help. For example, list some of the equations you have been trying and show some work.

I try this but i don't no if it is right
J=I/A=100*10^-9 /0.5*1
also J=(ne) V
then ne(q)=J/v
and then i take the q as the surface charge density
and it well = 5*10^-9

The units do not come out right at all in that last equation.

You know the current and that is just dq/dt. That is the same as saying dq charge passes by in a time dt. So draw a picture of how much charge passes by in a time dt, knowing the width of the belt and how fast it is moving.

Thanx Nickjer For your help I finally get it

## 1. What is surface charge density?

Surface charge density refers to the amount of electric charge that is present per unit area on the surface of an object. It is measured in units of coulombs per square meter (C/m2).

## 2. How is surface charge density calculated?

Surface charge density can be calculated by dividing the total charge on the surface of an object by the surface area of that object. It can also be calculated by taking the integral of the electric field over the surface.

## 3. What factors affect surface charge density?

The factors that can affect surface charge density include the amount of charge on the surface, the size and shape of the object, and the dielectric properties of the surrounding medium. Changes in any of these factors can impact the surface charge density on the object.

## 4. Why is it important to compute surface charge density on a belt?

Computing the surface charge density on a belt is important because it can help determine the amount of charge that is present on the belt, which can affect its performance. It can also help identify any potential safety hazards, such as electric shocks, that may be caused by the surface charge density.

## 5. How can surface charge density on a belt be measured in a laboratory setting?

Surface charge density on a belt can be measured in a laboratory setting using a variety of techniques, such as a Faraday cage or a Kelvin probe. These methods involve measuring the electric field at various points on the surface of the belt and using that information to calculate the surface charge density. Other methods, such as the capacitance method, can also be used to measure surface charge density on a belt.